Activation and inhibition of lipoprotein lipase in mixed monolayers of medium or long chain-triglycerides and phospholipids |
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Authors: | I Arimoto M Fujita H Saito T Handa K Miyajima |
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Institution: | (1) Faculty of Pharmaceutical Sciences Kyoto University Sakyo-ku Kyoto 606-01, Japan, JP |
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Abstract: | We evaluated the activation and inhibition effects of phosphatidylcholine (PC) and sphingomyelin (SM) on lipoprotein lipase
(LPL) for medium or long chain-triglycerides (TG) in monolayers at the air/water interface. Monolayers of medium chain-TG,
being in an expanded state at a surface pressure of 15 mN/m, showed low susceptibility to LPL in the subphase. Adding 50 mole%
of PC or SM into these monolayers reduced the partial molecular area of the TG and enhanced the LPL activity. Monolayers of
long chain-TG, being in a condensed state, showed high susceptibility of LPL either with or without PC. SM added to the long
chain-TG monolayers, however, inhibited the LPL action. We investigated the interaction between TG and phospholipid on the
basis of the collapse pressure-measurements of mixed monolayers. For medium chain-TG monolayers, PC and SM gave similar collapse
pressure-composition profiles. Contrary to this, SM gave a markedly higher collapse pressure of long chain-TG than PC: SM
stabilized the monolayer state of long chain-TG. These results suggested that I) orientation of the acyl chains of TG molecule
in a monolayer is crucial for the LPL activity, and that II) strong interaction between SM and long chain-TG retards the substrate-transfer
from the mixed monolayer to the catalytic pocket of LPL.
Received: 6 March 1996 Accepted: 19 July 1996 |
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Keywords: | Lipoprotein lipase inhibition phosphatidylcholine sphingomyelin triglyceride monolayer |
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